Wii-habilitation" — using Nintendo's Wii video game
system in rehabilitation therapy — continues to be
popular with health care workers looking to help patients
get through what some see as the pain and torture of
physical therapy. Now two engineers in APL's National
Security Technology Department have cranked that concept up
a notch. Bobby Armiger and Jacob Vogelstein have rewired
Nintendo's Guitar Hero III: Legends of Rock game to allow
amputees to rock out and get valuable training with
prosthetic prototypes at the same time.

Their gaming is part of the APL-led Revolutionizing
Prosthetics 2009 effort, funded by the Defense Advanced
Research Projects Agency, to develop a prosthetic arm that
will be controlled and also feel, look and perform like a
natural limb. So far the project has produced two
prototypes and has leveraged a surgical technique,
developed at the Rehabilitation Institute of Chicago by
Todd Kuiken, that reroutes the nerves that once controlled
an amputee's arm to remaining muscles. These "re-
innervated" muscles naturally amplify the nerve signals so
that electrodes placed against the skin can detect activity
and control the prosthetic arm.

The surgery has enabled patients to control the first
prototype arm and will eventually be used to control
individual fingers of the final prosthetic design. But for
the arm to operate correctly using these rerouted nerves,
the system must learn to interpret the patient's muscle
signals. The process is similar to training
voice-recognition software where, for example, you are
prompted to read the Gettysburg Address, except that
instead of analyzing tones, the APL system records and
classifies muscle twitches.

This training takes place in a Virtual Integration
Environment, another RP 2009 innovation. "In the VIE, an
animated on-screen arm mimics the patient's intended
movements in real time, based on inputs from the electrodes
attached to the user's residual muscles," Vogelstein
explains. "For the training, a patient sits in front of a
computer and an on-screen prompt tells them to 'flex your
wrist,' 'extend your wrist,' 'close your fist,' etc."

Calibrating the mechanical limbs to recognize and respond
properly to electrical signals in an amputee's residual
muscles is an exhausting and draining process, says
Armiger, who has been on the front lines of training the
system to respond naturally to the patient. "There is no
real interaction and no feedback," he says. "And there is
no encouragement for the patient to do more or do it
better."

The idea to adapt the game for amputees came to Armiger
while he was playing Guitar Hero at a party. He and
Vogelstein borrowed a colleague's copy of the game and
modified the controller with a soldering iron to allow it
to be controlled by the VIE. Then, button clicks were
substituted with muscle contraction signals as picked up by
the electrodes.

Last fall, Armiger and Vogelstein traveled to RP 2009
partner Duke University to test the rigged system on Iraq
veteran Jonathan Kuniholm, who lost his right hand to
shrapnel in 2005. With electrodes attached to what was left
of his arm, Kuniholm was able to operate the frets using
signals from his muscles.

The researchers found that playing a game is a far more
intuitive way to speed up the tedious calibration process
and make it more fun for volunteers. "It allows for large
numbers of rapid, dynamic movements that are more natural
and not stereotyped," Vogelstein says. "Ultimately we are
going to get more input and longer training cycles out of
patients — and that will translate to better and more
natural limb control."

Armiger and Vogelstein next want to adapt a tennis game to
train people with more radical amputations. "Eventually we
want to make our software open source so that people can
repurpose other games for rehabilitation," Armiger says.